1. Field of the Invention
The invention relates generally to the use of strings of coiled tubing to dispose flow actuated pumps into a wellbore and operation of such pumps.
2. Description of the Related Art
Downhole pumps are used to pump hydrocarbon fluids and/or water from subterranean locations. Electric submersible pumps (“ESPs”) require electrical power to be supplied to them from surface. A typical ESP assembly includes a centrifugal pump that is mounted to an electrical motor. A power cable extends from the surface to the motor of the ESP assembly.
Flow actuated pumps are also known which utilize a piston or plunger to flow fluid, as opposed to a centrifugal pumping mechanism. A flow actuated pump is described in U.S. Pat. No. 7,789,131 entitled “Hydraulic Pump System for Deliquifying Low Rate Gas Wells.” The '131 patent is owned by the assignee of the present invention and is hereby incorporated by reference in its entirety. The flow actuated pump described in the '131 patent uses a power fluid supplied from surface to operate the pumping mechanism rather than electrical power. Most flow actuated pumps return exhausted power fluid with the wellbore fluid (water, gas, etc.) being produced. However, some flow actuated pumps may have separate outputs for the exhausted power fluid and the wellbore fluid.
Dual-walled piping has been used in subsea applications to raise production fluid from a pump located on a seabed and not directly into a well. Such an arrangement is described in U.S. Patent Publication 2003/0170077 by Herd et al. However, dual-walled coiled tubing has not heretofore been successfully used in subterranean wellbores in conjunction with fluid driven or flow actuated pumps or for dewatering gas wells. The high pressure, high temperature conditions associated with a subterranean wellbore make the use of risers and flexible tubing impractical.